The present invention relates to a roll-forming apparatus with a sweep station adapted to impart multiple sweeps (i.e., non-uniform longitudinal curvatures) into a roll-formed beam as part of a continuous in-line process.
Roll-formed bumper beams have recently gained wide acceptance in vehicle bumper systems due to their low cost and high dimensional accuracy and repeatability. Their popularity has increased due to the ability to sweep (i.e., provide longitudinal curves) in the roll-formed beam sections in order to provide a more aerodynamic appearance. For example, one method for roll-forming a constant longitudinally curved beam is disclosed in Sturrus U.S. Pat. No. 5,092,512.
The aerodynamic appearance of vehicle bumpers is often further enhanced by forming a section of the front surface at ends of the bumpers rearwardly at an increased rate from a center of the bumper beam. This is typically done by secondary operations on the bumper beam. Exemplary prior art secondary operations for doing this are shown in Sturrus U.S. Pat. No. 5,092,512 (which discloses deforming/crushing ends of tubular beam), and are also shown in Sturrus U.S. Pat. No. 6,240,820 (which discloses slicing ends of a beam and attaching brackets), Heatherington U.S. Pat. No. 6,318,775 (which discloses end-attached molded components), McKeon U.S. Pat. No. 6,349,521 (which discloses a re-formed tubular beam), and Weykamp U.S. Pat. No. 6,695,368 and Reiffer U.S. Pat. No. 6,042,163 (which disclose end-attached metal brackets). However, secondary operations add cost, increase dimensional variability, and increase in-process inventory, and also present quality issues. It is desirable to eliminate the secondary operations required to form the bumper ends with increased rearward sweep. At the same time, vehicle manufacturers want to both maintain low cost and provide flexibility in bumper beam designs. Thus, there are conflicting requirements, leaving room for and a need for the present improvement.
It is known to provide computer controls for bending and roll-forming devices. See Berne U.S. Pat. No. 4,796,399, Kitsukawa U.S. Pat. No. 4,624,121, and Foster U.S. Pat. No. 3,906,765. It is also known to make bumper beams with multiple radii formed therein. For example, see Levy U.S. Pat. No. 6,386,011 and Japan patent document JP 61-17576. Still further, it is known to bend tubing and beams around the arcuate outer surface of a disk-shaped mandrel by engaging the tube to wrap the tube partially around the mandrel until a desired permanent deformation occurs. For example, see Miller U.S. Pat. No. 1,533,443 and Sutton U.S. Pat. No. 5,187,963. Nonetheless, it is important to understand that bumper beams for modern vehicles present a substantial increase in difficulty due to their relatively large cross-sectional size and non-circular cross-sectional shape, the high strength of materials used herein, the very tight dimensional and tolerance requirements of vehicle manufacturers, the cost competitiveness of the vehicle manufacturing industry, and the high speed at which modern roll-forming lines run.
Notably, existing sweep mechanisms on roll-forming equipment are often made to be adjustable. For example, Sturrus '512 discloses a manually adjustable sweep station. (See as Sturrus '512, FIGS. 10-11, and column 6, lines 1-9.) However, even though the sweep station is adjustable, it does not necessarily mean that the apparatus is able to manufacture beams having multiple sweep radii therein. For example, since the sweep station in the apparatus of Sturrus '512 is manually adjustable, as a practical matter it cannot be adjusted quickly enough to allow formation of regularly-spaced different curves in a single vehicle bumper beam section. Notably, bumper beams are usually only about 4 to 5 feet long and roll-forming line speeds can reach 4000 to 5000 feet per hour, such that any change in sweep must be accomplished relatively quickly and very repeatably. Certainly, non-uniform longitudinal curvatures cannot be uniformly repeated formed along a length of a continuous beam by manual means and further cannot productively and efficiently be made in high speed rollforming operations using slow-acting automated equipment. Accordingly, there remains a need for a method and roll-forming apparatus capable of manufacturing a roll-formed beam with different radii along its length “on the fly” (in other words simultaneously during continuous operation of the roll-forming process), where the method and apparatus do not require substantial secondary operations (or at least they require less secondary processing), such as cutting, fixturing, welding, secondary forming and/or post-roll-forming attachment of bracketry.
Renzzulla U.S. Pat. No. 6,820,451 is of interest for disclosing a power-adjusted sweep station. As best understood, the '451 patent discloses an adjustable sweep station for roll-forming a constant sweep into an open beam section, where an operator can adjust “on the fly” to maintain the constant sweep. (See Renzzulla '451, column 14, lines 1-7 and lines 42-45.) The '451 patent discloses a roll-forming apparatus where an upstream roller (16) is followed by an adjustable carriage adjustment assembly (14) that incorporates a primary bending roller (18) and an adjustable pressure roller (20) forming a first part of the sweep mechanism (for coarse adjustment of sweep), and also an auxiliary roller (22) forming a second part (for fine adjustment of sweep) (see Renzzulla '451, column 14, lines 20-22.). In the '451 patent, the lower primary roller (18) (i.e., the roller on the downstream/convex side of the swept beam) is preferably positioned above the line level of the beam being roll-formed (see FIG. 1, “flexing roller 18 is vertically higher than the line level”, see column 10, line 65 to column 11 line 1.) The second roller (20) (i.e., the roller on the concave side of the swept beam) is supported for adjustable arcuate movement around the axis (shaft 90) of the first roller (see FIGS. 15-16) to various upstream-adjusted positions for putting pressure on the continuous roll-formed beam. Actual flexure of the beam occurs upstream of the rollers (18/20) at location 143. (See column 12, line 45-46.) A control assembly (130) is adapted to move the roller (20) along its arcuate path of adjustment. (See column 8, line 62+, and see FIGS. 1-2). An auxiliary carriage assembly (110) is positioned to adjust roller (22) on the primary carriage assembly (14) and is adjustable by operation of an adjustment assembly (137). The patent indicates that both adjustments can be done “on the fly” (see column 14, line 4), and that the primary and auxiliary assemblies can be adjusted for coarse and fine sweep adjustments, respectively. (See column 14, line 22).
Although the device disclosed in the '451 patent can apparently be power-adjusted while the roll-forming apparatus is running, the present inventors find no teaching or suggestion in the '451 patent for providing a controlled/timed adjustment function for creating multiple sweeps in a single beam section, nor coordinated control function for repeatedly adjusting the device to provide a repeated series of dissimilar sweeps (i.e., different radii) at selected relative locations within and along the length of a single bumper beam segment (e.g., within a span of about 4 to 5 feet as measured along a length of the roll-formed continuous beam). Further, there is no teaching in the '451 patent to form a multi-swept beam using a computer controlled sweep apparatus in continuation with a coordinated computer-controlled cut-off device adapted to cut off individual bumper beam sections from the continuous beam at specific locations related to particular sweep regions. Further, based on the density of threads suggested by the FIGS. 1-2 (and also based on the lack of any discussion in the '451 patent regarding automated “cyclical” adjustment), it appears that the device of the '451 patent suffers from the same problem as manually adjustable sweep stations—i.e., that it cannot be adjusted fast enough to cause multiple sweeps within a 4 to 5 foot span along the continuous roll-formed beam, given normal relatively fast linear speeds of roll-forming mills. Further, its disclosure focuses on maintaining a constant sweep. (See Renzzulla '451, column 10, lines 54-55 where it states the sweep forming assembly is “to impart a permanent bumper curvature to the bumper structure.”)
There is potentially another more fundamental problem in sweep station of the Renzzulla '451 patent when providing tight sweeps (i.e., sweeps with short radii) along a continuous beam. The '451 patent focuses on a sweep station where a first relatively stationary (primary) forming roller (18) is positioned above a line level of the continuous beam (see column 10, line 65 to column 11 line 1) to deflect a continuous beam out of its line level, and discloses a second movable/adjustable pressure roller (20) that is adjustable along an arcuate path around the axis of the first relatively-stationary (primary) roller (18) in order to place bending forces at a location (143) forward of (upstream of) the primary roller (18) . . . the upstream location (143) being generally between and upstream of the primary roller (18) and the upstream support roller (16). (See FIG. 16, and column 12, lines 45-46). As the sweep mechanism of the '451 patent is adjusted to form tighter and tighter sweeps (i.e., sweeps with increasingly smaller radii), the location (143) of bending potentially moves even farther upstream and away from the primary roller (18). By forcing flexure and deformation of the beam to occur at an unsupported upstream location (143), the beam walls effectively are allowed to bend in an uncontrolled fashion. This makes it very it difficult to control twisting and snaking, difficult to control undesired warping and wandering, and also difficult to control dimensional variations. These variables combine and lead to unpredictability of deformation in the beam and the beam walls. In other words, as the unsupported distance increases (i.e., as tighter sweeps are formed), the problem of uncontrolled movement and deflection of the beam walls becomes worse . . . potentially leading to dimensional and quality problems.
Compounding this problem is the fact that the diameter of rollers 16 force the rollers 16 to be positioned away from the rollers 18 and 20 . . . which results in the contact points of the rollers 16 and 18 against the beam to be a relatively large distance equaling basically the distance between the axles on which the rollers 18 and 20 rotate. This large unsupported distance allows the walls of the roll-formed beam to wander and bend uncontrollably as deformation occurs in this area of no support.
The above-noted problems are made worse when a tubular beam is swept. Specifically, the problems of twisting and snaking, poor control of undesired warping and wandering, and also uncontrolled dimensional variations become even worse when a tubular beam is roll formed and swept. This is due in part to the increased strength of the beam due to the tubular shape, but also due to the difficulty in supporting the inner surfaces of the beam walls, due to the closed tubular shape. If the inside of the walls cannot be engaged and controlled, it tends to wander unacceptably, particularly for large beam sections deformed into tight swept curvatures.
Thus, a system having the aforementioned advantages and solving the aforementioned problems is desired.